This section provides background information related to the present disclosure and is not necessarily prior art.
A significant proportion of the cost of a turbocharger assembly is contained within the turbine housing. The turbine housing receives hot gas from an exhaust system, channels it through a volute section to a turbine, and finally directs turbine discharge gases to the rest of the exhaust system. A material or materials from which the turbine housing is formed should be able to withstand a maximum expected temperature due to the hot exhaust gases. For many applications the high exhaust gas temperature causes the turbine housing temperature to exceed the working limit of traditional low cost ferritic cast irons, and as a result, highly alloyed, temperature resistant materials such as Ni-Resist (D5S) or austenitic stainless steels (e.g. 1.4848 and 1.4849) are often required. These high alloy materials are expensive and add substantial cost to the overall assembly.
In order to keep the cost of a turbine housing low, it may be desirable to make the turbine housing from a low cost material such as ferritic cast iron or aluminum. A material such as aluminum may not be heat resistant enough to operate at the working temperatures of most turbine housings, and may require active cooling to keep the aluminum housing within practical temperature limits. For many aluminum alloys, this means keeping the aluminum material well below 300° C. at all locations.
As the cost of expensive alloys such as nickel continues to rise in the future, there will be increased interest by the engine and turbocharger manufacturers to reduce the cost of the turbocharger system by employing low cost and/or lightweight materials (possibly with active cooling if required) for the turbine housing. It is to this end that the present disclosure is made.